1. Field of the Invention
The present invention relates to an alternator or a rotating electrical machine to be installed in an automobile.
2. Description of Related Art
An alternator for vehicle or a rotating electrical machine includes a stator and a rotatably supported rotor. The stator is constituted with a stator core with numerous slots formed therein over the entire periphery thereof along the circumferential direction and a stator coil disposed inside the numerous slots. While the stator coil needs to be inserted in the numerous slots formed at the stator core to achieve this structure, the stator coil cannot be inserted in the slots through a simple process, posing a significant obstacle to achieving better productivity. For this reason, an alternator or a rotating electrical machine assuming a structure that does not include any slots and has the stator coil disposed along the circumference of a rotational axis can be manufactured more easily.
Structures with the stator coil disposed on a plane perpendicular to the rotational axis, instead of winding the stator coil through slots formed at the stator core, are known in the related art. Japanese Laid Open Patent Publication No. 2005-151785 (patent reference literature 1) and Japanese Laid Open Patent Publication No. H2-159949 (patent reference literature 2) each discloses such a structure.
For instance, the synchronous generator disclosed in patent reference literature 1 includes a rotor constituted with three separate permanent magnets each corresponding to one of; a U-phase, a V-phase and a W-phase, and stators each paired up with one of the three permanent magnets in the U-phase, the V-phase and the W-phase. Since the power output of this synchronous generator fluctuates greatly under conditions in which the rotation rate changes significantly, its structure cannot be adopted in, for instance, alternators for vehicles.
Patent reference literature 2 discloses an alternator for vehicle that includes an annular stator coil. While an alternator for vehicle must assure high output, a technology for obtaining high output is not described in relation to the alternator for vehicle disclosed in the literature.
While a rotating electrical machine assuming a structure with a stator coil disposed along the circumference of the rotational axis is often utilized in an extremely small motor that does not impose rigorous requirements with respect to the output characteristics at present, such a rotating electrical machine is not adopted in applications requiring high output characteristics. In particular, the structure has not been adopted in the compact rotating electrical machines for vehicle required to assure high efficiency. In addition, it has not been adopted for practical use in alternators for vehicles with greatly variable rotation speeds, which are, nevertheless, required to provide high performance over the full range of rotation speeds, from low speed to high speed.
The present invention is to provide a rotating electrical machine or an alternator that assures outstanding output characteristics.